Posted 05 September 2006 - 02:58 AM
The floor and the walls need to be evenly lit. Also...at what stop would you decide to place the wall and floor. Would you rather have the subject lit below the stop on the wall or have the wall be darker than the subject?
Posted 05 September 2006 - 06:21 AM
to set up a green screen is more than just a half days of work. lots of estimations and calculations have to be done to find the right setup that works best with your space.
first the purpose should be determined. what will be the main use?
also, what material you get for your greenscreen? i was forced to shoot with a lot of terrible green painted walls and wood panels in my time that prove to be a nightmare.
the basic idea is to light it evenly. but thats easy to say, hard to achieve. if you are using fabric which is likely to wrinkle especially when windmachines are used (i had that) this problem becomes more prominent. the distance between for- and background is a key, also how deep is the stage, is it possible to position actors far away so the screen is likely to be put out of focus?
also what cameras/ optics will mostly be used? if you are shooting on a large neg i.e 35mm you are on the safer side than with tiny ccds since your dof is reduced, and the optics perform well almost wide open (i recommend for calculations to use one stop less than wide open,say T3.5 on a 2.8). thats your key light for the forground which should also be the illumination for the background. as a rule of thumb i set my key lights for the foreground the same as the screen. the separation is achieved using backlight on the forground. so you need to rig those lights as well. if you use an extreme of T3.5 at ASA100 and some highspeed photography, lets say 150fps you get the level of illumination your light setup must have on the actors as well as on the screen.
here in switzerland we tend to use round horizon halogenic lamps that can be mounted to the ceiling and put on the floor. they thow an evenly light carpet on the screen at powers of up to 5K at 3200K, but the problem is that the carpet tends to flat out. you can help it with the use of flobanks that are balanced to your horizon lights. on smaller screens i used a lot of bounced off appollos by arri. they were 2K. using a scrim i bounced them off some large styrofoam panels using big flags to avoid that the light areas intersect.
i could go on forever, even with my amateurish knowledge. but to light a greenscreen in a general way is a book with seven seals...
Posted 06 September 2006 - 04:29 PM